For BZ1206936 [1] we started adding resume= kernel command line by
default [2] in fedora installs. This is causing issues for ostree
based systems, which I haven't fully investigated yet, but figured
I would ask the question:
Is resume=/path/to/swap something we really want on server installs
like Fedora Server and Fedora Atomic Host?

It seems *unnecessary*, but I'm not sure I understand what problems it
causes. Could you got into more detail there?
I can't see anyone putting a Server or Atomic Host into hibernation,
though. Does this just direct the kernel where that should go if
hibernation is requested, or does it reserve space or something for
it?

On Wed, Oct 17, 2018 at 11:27 PM Dusty Mabe
<dusty(a)dustymabe.com&gt; wrote:
>
> For BZ1206936 [1] we started adding resume= kernel command line by
> default [2] in fedora installs. This is causing issues for ostree
> based systems, which I haven't fully investigated yet, but figured
> I would ask the question:
>
> Is resume=/path/to/swap something we really want on server installs
> like Fedora Server and Fedora Atomic Host?
It seems *unnecessary*, but I'm not sure I understand what problems it
causes. Could you got into more detail there?
I can't see anyone putting a Server or Atomic Host into hibernation,
though. Does this just direct the kernel where that should go if
hibernation is requested, or does it reserve space or something for
it?

AFAIK it tells the kernel where to look for a hibernation image to
restore from - so it normally points at one of the swap partitions.
If the kernel finds a hibernation image on the specified device then
it will restore that and switch to it otherwise it will just continue
booting as normal.
Tom
--
Tom Hughes (tom(a)compton.nu)
http://compton.nu/

I can't see anyone putting a Server or Atomic Host into
hibernation,
though. Does this just direct the kernel where that should go if
hibernation is requested, or does it reserve space or something for
it?

There might be some use for it for VMs....
--
Matthew Miller
<mattdm(a)fedoraproject.org&gt;
Fedora Project Leader

On Thu, Oct 18, 2018 at 07:58:33AM -0400, Stephen Gallagher wrote:
> I can't see anyone putting a Server or Atomic Host into hibernation,
> though. Does this just direct the kernel where that should go if
> hibernation is requested, or does it reserve space or something for
> it?
There might be some use for it for VMs....

On Thu, Oct 18, 2018 at 8:29 AM Matthew Miller
<mattdm(a)fedoraproject.org&gt; wrote:
>
> On Thu, Oct 18, 2018 at 07:58:33AM -0400, Stephen Gallagher wrote:
> > I can't see anyone putting a Server or Atomic Host into hibernation,
> > though. Does this just direct the kernel where that should go if
> > hibernation is requested, or does it reserve space or something for
> > it?
>
> There might be some use for it for VMs....
Doesn't the hypervisor do that itself for VMs?

You have a choice, but most people do use hypervisor save/restore. It
is rare to see guest S3/S5 save/restore used in VMs.
The hypervisor initiated save/restore VM state to a file will work with
any OS, as it is transparent to the guest. The saved state can also be
explicitly managed by the host mgmt tools, letting you do snapshotting
and rollback of state, if you combine memory state with file snapshots.
The key downside is that it is transparent to the guest, so when you
restore the guest, its clock will be wrong and needs fixing / catching
up.
With guest initiated save/restore you're not using any additional host
resources and its all confined in the guest execution environment. The
guest knows to update its clock upon restore since it is aware of what
is happening. The downside is that not all guest OS are reliable at doing
S3/S5, and for that matter not all hypervisors will actually advertize
S3/S5 support in their BIOS. IIRC, RHEL KVM explicitly disables this.
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|

> > There might be some use for it for VMs....
> Doesn't the hypervisor do that itself for VMs?
You have a choice, but most people do use hypervisor save/restore. It
is rare to see guest S3/S5 save/restore used in VMs.

On Wed, Oct 17, 2018 at 11:27 PM Dusty Mabe
<dusty(a)dustymabe.com&gt; wrote:
>
>
> For BZ1206936 [1] we started adding resume= kernel command line by
> default [2] in fedora installs. This is causing issues for ostree
> based systems, which I haven't fully investigated yet, but figured
> I would ask the question:
>
> Is resume=/path/to/swap something we really want on server installs
> like Fedora Server and Fedora Atomic Host?
>
It seems *unnecessary*, but I'm not sure I understand what problems it
causes. Could you got into more detail there?

Yeah. https://pagure.io/atomic-wg/issue/513#comment-536736
Basically for some reason on ostree based systems the LV isn't available
before the systemd unit for hibernation runs and boot has to wait for that
unit to timeout before continuing. I'm still investigating why that is.
>
> I can't see anyone putting a Server or Atomic Host into hibernation,
> though. Does this just direct the kernel where that should go if
> hibernation is requested, or does it reserve space or something for
> it?
>

On 10/18/2018 07:58 AM, Stephen Gallagher wrote:
> On Wed, Oct 17, 2018 at 11:27 PM Dusty Mabe <dusty(a)dustymabe.com&gt; wrote:
>>
>>
>> For BZ1206936 [1] we started adding resume= kernel command line by
>> default [2] in fedora installs. This is causing issues for ostree
>> based systems, which I haven't fully investigated yet, but figured
>> I would ask the question:
>>
>> Is resume=/path/to/swap something we really want on server installs
>> like Fedora Server and Fedora Atomic Host?
>>
>
> It seems *unnecessary*, but I'm not sure I understand what problems it
> causes. Could you got into more detail there?
Yeah. https://pagure.io/atomic-wg/issue/513#comment-536736
Basically for some reason on ostree based systems the LV isn't available
before the systemd unit for hibernation runs and boot has to wait for that
unit to timeout before continuing. I'm still investigating why that is.

It does sound like anaconda could be more picky here for when it adds
this. Additional to the atomic/ostree case, if you have secure boot
enabled it's useless to add, if your swap is smaller than your memory
it's useless to add, etc.
kevin